Dual mode system for detecting occupancy of a room

ABSTRACT

A method and system improve on the accuracy of and power consumption of occupancy detection systems. Embodiments may provide a dual mode system that includes a passive infrared sensor with low power consumption and a RADAR-based sensor with higher power consumption that is only powered when the system determines a room is occupied with the passive sensor and no new movement is detected after a threshold duration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 U.S.C. § 119(e) of U.S.application Ser. No. 17/510,154 filed Oct. 25, 2021, and U.S.application Ser. No. 16/857,585 filed Apr. 24, 2020 which claimedpriority to U.S. Provisional Application No. 62/840,028 filed Apr. 29,2019, which are hereby incorporated by reference herein in its entirety.

BACKGROUND

The embodiments herein relate generally to detection systems, and moreparticularly, to a dual mode system for detecting occupancy of a room.

Commonly used occupancy sensors do not adequately the detect presence ofsedentary people, who are for example reading or typing. Thismisdetection can lead to lights and HVAC switching systems off while aroom is occupied. People have to wave and stand to get the system toacknowledge their presence and turn the systems back on. Because of thisannoyance, users often either disable the occupancy sensors or use themwith very long time delays. The energy savings are thus less than theycould be with a more accurate occupancy sensor.

Some systems use a RADAR based sensor. However, standalone RADAR systemsare too power-hungry which may be impractical to use when a roomoccupancy detector is operated by battery. As may be expected, thebattery life is short-lived and may require frequent batteryreplacement.

SUMMARY

In one aspect of the subject technology, a system for detectingoccupancy in a room is disclosed. The system includes an infraredsensor, a RADAR based sensor, and a processor. The processor isconnected to the infrared sensor and connected to the RADAR basedsensor. The processor is configured to: receive a signal from theinfrared sensor detecting movement in the room, determine whether afirst threshold duration has passed since a most recent signal from theinfrared sensor detecting movement in the room has been received,trigger operation of the RADAR based sensor based on the first thresholdduration having passed since the most recent signal from the infraredsensor detecting movement in the room was received, wherein the RADARbased sensor is on for a second threshold duration that is less than thefirst duration; and determine whether the RADAR based sensor detects apresence of a person in the room, turn off the RADAR based sensor inresponse to at least one of: detecting the presence of a person in theroom, or not detecting the presence of a person in the room during thesecond threshold duration, and switch back to receiving the signal fromthe infrared sensor.

In another aspect, a system for detecting occupancy in a room isdisclosed. The system includes an infrared sensor, a RADAR based sensor,and a processor. The processor is connected to the infrared sensor andconnected to the RADAR based sensor. The processor is configured to:receive, by a processor, a signal from an infrared sensor detectingmovement in the room; determine, by the processor, whether a firstthreshold duration has passed since a most recent signal from theinfrared sensor detecting movement in the room has been received;trigger, by the processor, operation of a RADAR based sensor based onthe threshold duration having passed since the most recent signal fromthe infrared sensor detecting movement in the room was received; anddetermine, by the processor, whether the RADAR based sensor detects apresence of a person in the room. In response to the RADAR based sensordetecting a presence of a person in the room, the processor deactivatesthe RADAR based sensor and checks the infrared sensor again for movementin the room. The processor determines whether a second thresholdduration has passed since the RADAR based sensor detected the presenceof a person in the room in the event the infrared sensor does not detectmovement in the room, and re-activates the RADAR based sensor.

In yet another aspect, a method for detecting occupancy in a room isdisclosed. The method includes operating an infrared sensor to detect apresence of a person in the room. The operation of the infrared sensordraws a first power level from a battery. A processor receives a signalfrom the infrared sensor detecting movement in the room. The processordetermines whether a first threshold duration has passed since a mostrecent signal from the infrared sensor detecting movement in the roomhas been received. The processor triggers operation of a RADAR basedsensor based on the first threshold duration having passed since themost recent signal from the infrared sensor was received. Operation ofthe RADAR based sensor draws a second power level from the battery thatis substantially higher than the first power level. The processordetermines whether the RADAR based sensor detects a presence of one ormore people in the room or an absence of persons in the room. Operationof the RADAR based sensor is changed into a sleep mode in response tothe RADAR based sensor detecting the presence of one or more persons inthe room or the absence of persons in the room. The sleep mode drawsless power than the first power level and substantially less power thanthe second power level. The infrared sensor is operated again to detectmovement in the room, drawing the first power level from the battery.

BRIEF DESCRIPTION OF THE FIGURES

The detailed description of some embodiments of the invention is madebelow with reference to the accompanying figures, wherein like numeralsrepresent corresponding parts of the figures.

FIG. 1 is a flowchart of a method for operating a dual mode system fordetecting occupancy in a room in accordance with an embodiment of thesubject technology.

FIG. 2 is a block diagram of a dual mode system for detecting occupancyin a room in accordance with an embodiment of the subject technology.

FIG. 3 is a block diagram of a dual mode system for detecting occupancyin a room using a system on chip architecture in accordance with anotherembodiment of the subject technology.

FIG. 4 is a flowchart of a method for detecting occupancy in a room inaccordance with an embodiment of the subject technology.

FIG. 5 is a flowchart of a method for detecting occupancy in a room inaccordance with another embodiment of the subject technology.

FIG. 6 is a flowchart of a method for detecting occupancy in a room inaccordance with another embodiment of the subject technology.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

Broadly, embodiments of the subject technology increase the accuracy ofoccupancy detection while providing cost-effective use of energy topower occupancy detection systems. In general, the subject technologyuses a dual mode system which uses a low energy consuming detector untilconditions warrant the use of a higher energy consuming detector toverify occupancy or the lack there of. In an exemplary embodiment, thesystem includes an infrared sensor and a RADAR based sensor. Theinfrared sensor consumes less power to operate than the RADAR baseddetector. FIG. 1 shows a process for detecting occupancy of a roomaccording to an exemplary embodiment. The infrared sensor may be thedefault detection element and may be in operation until, for example,the infrared sensor does not detect movement in the room for a thresholdduration (T1). In response to the infrared sensor not detecting thepresence of a person in the room, the RADAR based sensor may betriggered to turn on. If the RADAR based sensor confirms that the roomdoes not register movement, the system may confirm the room is vacant.Rooms in a vacant state may have resources connected to the room turnedoff (for example, lights, heating/air conditioning, etc.). In the vacantstate, the infrared sensor may operate and if the infrared sensordetects motion, the system may determine the room is occupied and mayassume the room remains occupied until the infrared sensor has notregistered movement again for the threshold duration and the RADAR basedsensor confirms whether or not the room is vacant.

In the description below, embodiments may determine whether a person inthe room is exhibiting gross or large motion or is sedentary, if presentat all. Gross or large motion may refer to body movement that includesmovement of the whole body (for example, walking about), movement ofappendages (for example, waving arms, raising hands, stretching).Sedentary or stationary people may refer to persons that are seated orstanding and whose detectable motion is primarily breathing withoutgross or large motion activity. Sedentary activity may include shortrange activity (for example, speaking, typing, head movements, fingermovements, etc.).

Referring now to FIG. 2 , a dual mode system for detecting occupancy ina room is shown according to an exemplary embodiment. In someembodiments, the infrared motion sensor may be passive, which thusconsumes less power. The infrared sensor may be referred to as the PIRsensor (passive infrared) in the description below, however it will beunderstood that in some embodiments, other infrared, other passivesensors, or other lower power consumption sensors may be used. In someembodiments, the system may be adjunct to the operating elements of theroom. The system may have its own power source, for example, a battery.The system may include a processor (for example, a microcontroller(MCU)) connected to the infrared sensor and to the RADAR based sensor.In some embodiments, the processor may be located on a system on chipmodule (SOC) (See FIG. 3 ) which may provide a conveniently smallpackage for controlling the detection system. In other embodiments, theprocessor is part of a larger computing device.

The RADAR based sensor may be a continuous wave Doppler type that cansense respiratory motion. Operation of a Doppler RADAR sensor may be asfollows: in some embodiments, a single-ended RADAR may be used, and inother embodiments, a quadrature RADAR may be used. The system maydigitize the signal phase shift, which is related to the motion in theroom. In some embodiments, signal conditioning circuitry filters thisdata to isolate the frequency range in which physiological signals(respiration, heartbeat) and their first few harmonics are present. Inother embodiments, the signal conditioning performs anti-aliasingfiltering and/or removes DC offsets. In some embodiments, both types ofsignal conditioning (isolating the frequency range and anti-aliasing)may be used. These conditioned signals are digitized and used foranalysis.

Generally speaking, the RADAR based sensor may operate for a specificamount of time, and then may be deactivated until the system indicatesit should be powered again. When a time has passed after the PIRdetector has sensed motion, the Doppler RADAR sensor may be used todetermine whether the room is vacant or if it is occupied by astationary person.

Once the presence of a stationary person is confirmed, the system mayassume that the room continues to be occupied by a sedentary personuntil the PIR detects a large motion. Once the room is confirmed vacantby the RADAR based sensor, the system may assume that the room remainsvacant until the PIR sensor detects large motion. Utilizing theassumption that, for example, a large motion is required for a person toenter or exit the room, the RADAR based sensor may be used minimally.Because the RADAR based sensor consumes far more power than the PIRsensor, minimizing the frequency with which the RADAR based sensor isused is helpful to reduce the system's power consumption such thatbattery operation is possible.

Referring now to FIG. 4 , a method of detecting occupancy in a room isshown according to an exemplary embodiment. Generally, the methoddetermines whether a room being monitored is in an occupied or vacantstate. The infrared sensor may be continuously operating checking formotion. Until the infrared sensor detects motion, the room may beconsidered vacant. Once movement is detected, the process may assumethat a person is in the room. The process may continue to check formotion detected by the infrared sensor. If motion is not detected for athreshold time (which may be an adjustable setting) (T1) after theprevious (most recent) movement detected, the process may triggeractivation of the RADAR based sensor. If the RADAR based sensor does notdetect movement, the process may signal that the room is vacant. TheRADAR based sensor may be turned off and the method may resumemonitoring signals from the infrared sensor. If the RADAR based sensordetects movement, the room may be flagged as occupied. In someembodiments, the RADAR based sensor may be turned off when the room isoccupied, and the method may resume using the infrared sensor to detectgross motion in the room before checking again with the RADAR basedsensor.

As will be appreciated, the RADAR based sensor may detect more subtlemovements such as breathing when people are sedentary in a room at theexpense of higher power consumption. Referring now to FIG. 5 , a methodfor detecting occupancy in a room is shown according to anotherembodiment. The method in FIG. 5 is similar to the method in FIG. 4except that after the RADAR based sensor detects an occupant, the systemperiodically uses the RADAR based sensor to confirm that the room isstill occupied by a sedentary occupant.

In the method, if there has been at least T1 minutes since the PIRsensor last sensed motion, the room may be flagged as vacant if theRADAR based sensor has been activated since then and has not sensed anyoccupants. In the vacant state, only the PIR sensor is active, and theother components may be in a low power “sleep mode” to reduce powerconsumption (for example, as shown seen in FIG. 6 ). If the PIR sensordetects motion, the state becomes “Occupied—PIR.” Otherwise, the stateremains “Vacant”.

In the Occupied—PIR state, the PIR sensor has sensed motion within thelast period T1. When the PIR senses motion, the processor activates tolog the motion and starts a clock on T1. Each time the PIR sensordetects motion, the clock on T1 may reset. When a time T1 has passedsince the PIR sensor last detected motion, the RADAR sensor isactivated. If the RADAR based sensor detects the presence of a person,the state becomes “Occupied-Radar.” If the RADAR based sensor does notdetect the presence of a person, the state becomes “Vacant”.

In the Occupied—Radar state, it has been at least T1 minutes since thePIR sensor has sensed motion, and the last RADAR based sensormeasurement indicates the presence of a person. In this state, the PIRsensor may remain active. If the PIR sensor detects motion, the statereturns to Occupied-PIR state. In some embodiments, when in theOccupied—RADAR state, if the PIR sensor does not detect motion, for T2minutes after the RADAR detected an occupant, the RADAR based sensor isactivated again to confirm the presence of a sedentary person. (T2>T1)If the RADAR based sensor detects presence, the method may remain inthis state, with the timer for T2 reset. If the RADAR based sensor doesnot detect motion, the state may change to vacant. In other embodiments,if the RADAR based sensor does not detect motion, it may repeat themeasurement, and if neither measurement detects the presence of aperson, the state may change to vacant.

When the RADAR based sensor is activated, it may be operated for aperiod T3, in which multiple breathing cycles can be detected. In someembodiments, T3 may be 30 seconds. In some embodiments, T3 may be oneminute. In some embodiments T3 may be 15 seconds. The interval T3 may beselected to optimize power consumption versus accuracy of detection.

Referring now to FIG. 6 , an embodiment of a state machine for aprocessor is illustrated. When the state is vacant, the processor is ina “sleep mode” waiting for an input from the PIR sensor. The currentconsumption in “sleep mode” is very low, for example 0.4 uA.

When the system enters the OCCUPIED state, an indication of occupancymay be transmitted via the communication/control circuitry. When thesystem enters the VACANT state, an indication of vacancy may betransmitted via the communication/control circuitry. In someembodiments, the status is periodically sent in the absence of thestatus change in a “handshake” with the unit with which it iscommunicating.

When the PIR sensor detects motion and wakes the processor, theprocessor communicates the new “occupied” state via WiFi, and the powerconsumption during communication may become 20 mA, but communication isonly needed for about 1 second.

Following communication, the processor may move into a “monitoring”state. The task scheduler is active. The processor may time how long ithas been since the most recent indication of motion from the PIR sensor.The current consumption in “monitoring” mode is for example, 1.3 uA. Inthe embodiment described, this state lasts 5 minutes from the mostrecent PIR signal.

After the 5 minutes from the most recent PIR signal, the system mayenter the “PIR Vacancy” state. The RADAR and signal processing may beactivated, and current consumption is about 20 mA. This state lasts for20 seconds in this embodiment. The processor analyzes the RADAR signaland if respiration is detected, the state returns to the “monitoring”state. If respiration is not detected, the state returns to the “vacant”state, and the change in state is communicated.

In some embodiments, the computing device controlling the system mayoperate the processes described above in the general context of computersystem executable instructions, such as program modules, being executedby a computer system. The computing device may typically include avariety of computer system readable media. Such media could be chosenfrom any available media that is accessible by the computing device,including non-transitory, volatile and non-volatile media, removable andnon-removable media. The system memory could include random accessmemory (RAM) and/or a cache memory. A storage system can be provided forreading from and writing to a non-removable, non-volatile magnetic mediadevice. The system memory may include at least one program producthaving a set (e.g., at least one) of program modules that are configuredto carry out the functions of embodiments of the invention. The programproduct/utility, having a set (at least one) of program modules, may bestored in the system memory. The program modules generally carry out thefunctions and/or methodologies of embodiments of the invention asdescribed above.

As will be appreciated by one skilled in the art, aspects of thedisclosed invention may be embodied as a system, method or process, orcomputer program product. Accordingly, aspects of the disclosedinvention may take the form of an entirely hardware embodiment, anentirely software embodiment (including firmware, resident software,micro-code, etc.) or an embodiment combining software and hardwareaspects “system.” Furthermore, aspects of the disclosed invention maytake the form of a computer program product embodied in one or morecomputer readable media having computer readable program code embodiedthereon.

Aspects of the disclosed invention are described above with reference toblock diagrams of methods, apparatus (systems) and computer programproducts according to embodiments of the invention. It will beunderstood that each block of the block diagrams, and combinations ofblocks in the flowchart illustrations and/or block diagrams, can beimplemented by computer program instructions. These computer programinstructions may be provided to the processing unit of a general-purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer or other programmabledata processing apparatus, create means for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

Persons of ordinary skill in the art may appreciate that numerous designconfigurations may be possible to enjoy the functional benefits of theinventive systems. Thus, given the wide variety of configurations andarrangements of embodiments of the present invention the scope of theinvention is reflected by the breadth of the claims below rather thannarrowed by the embodiments described above.

What is claimed is:
 1. A method for detecting occupancy in a room,comprising: operating an infrared sensor to detect a presence of aperson in the room, wherein the operation of the infrared sensor draws afirst power level from a battery; receiving, by a processor, a signalfrom the infrared sensor detecting movement in the room; determining, bythe processor, whether a first threshold duration has passed since amost recent signal from the infrared sensor detecting movement in theroom has been received; triggering, by the processor, operation of aRADAR based sensor based on the first threshold duration having passedsince the most recent signal from the infrared sensor detecting movementin the room was received, wherein operation of the RADAR based sensordraws a second power level from the battery that is substantially higherthan the first power level; determining, by the processor, whether theRADAR based sensor detects a presence of one or more persons in the roomor an absence of persons in the room; in response to the RADAR basedsensor detecting the presence of one or more persons in the room or theabsence of persons in the room, changing operation of the RADAR basedsensor into a sleep mode, wherein the sleep mode draws less power thanthe first power level and substantially less power than the second powerlevel; and operating the infrared sensor again to detect movement in theroom, drawing the first power level from the battery.
 2. The method ofclaim 1, wherein the operation of the RADAR based sensor is for a secondthreshold duration before the change to the sleep mode.
 3. The method ofclaim 1, wherein operation of the infrared sensor remains active duringoperation of the RADAR based sensor.
 4. The method of claim 1, whereinthe operation of the infrared sensor is for more than one minute and theoperation of the RADAR based sensor is for one minute or less than oneminute.
 5. The method of claim 1, further comprising placing theprocessor into the sleep mode in response to the RADAR based sensordetecting the absence of persons in the room.
 6. The method of claim 5,further comprising waking the processor up from the sleep mode in theevent the infrared sensor detects movement.